Variable displacement gerotor pump

ABSTRACT

A variable displacement pump having an inner rotor (gerotor) and an outer rotor is disclosed. Advantageously, the pump provides a movable outer rotor capable of changing the amount of fluid transferred from an inlet to an outlet. Optionally, a biasing member is connected to the outer rotor for preventing movement of the outer rotor below a predetermined amount of pressure at the outlet.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional Patent Application No. 60/788,324 entitled “VARIABLE DISPLACEMENT PUMP” filed on Mar. 31, 2006; U.S. Provisional Patent Application No. 60/849,659 entitled “VARIABLE DISPLACEMENT GEROTOR PUMP” filed on Oct. 5, 2006; U.S. Provisional Patent Application No. 60/849,673 entitled “VARIABLE DISPLACEMENT GEROTOR PUMP” filed on Oct. 5, 2006; U.S. Provisional Patent Application No. 60/850,466 entitled “VARIABLE DISPLACEMENT GEROTOR PUMP” filed on Oct. 10, 2006; and U.S. Provisional Patent Application No. 60/850,666 entitled “VARIABLE DISPLACEMENT GEROTOR PUMP” filed on Oct. 10, 2006, each of which is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention generally relates to an oil pump for a vehicle, and more particularly, to a variable displacement gerotor pump.

BACKGROUND OF THE INVENTION

Combustion engine vehicles require lubrication systems designed to deliver clean oil at the correct temperature and pressure to the engine. The oil pump is the center of the lubrication system and pumps oil from the oil reservoir through a wire screen to strain out any large particles and then through a filter to clean the oil. The oil is pumped to different parts of the engine to assist in cooling and lubrication before returning the oil to the oil reservoir, to continue the process.

Known oil pumps are designed to deliver oil in greater quantities and pressures than the engine actually requires. Typically, the drive element of a vehicle oil pump is coupled to the crankshaft so that the oil pump runs continuously while the engine is running. Such a continuously running oil pump provides consistently greater quantities of oil to the engine than are required. In order to maintain constant oil pressure, a pressure-regulating valve is installed in the oil pump or the engine block. The valve allows excess oil pressure to bleed off. However, the valve is designed with narrow tolerances and foreign material entering the valve hinders the operation of the valve or destroys the valve.

One type of pump frequently utilized as an oil pump is an internal tooth gear pump, or gerotor pump. The gerotor pump is a positive displacement pump that delivers a fixed amount of fluid per engine revolution. A gerotor pump consists of an inner rotor (gerotor) and an outer rotor. During a first part of the rotation cycle, the area (e.g. voids or chambers) between the inner and outer rotor increases to create vacuum suction to intake the lubrication fluid, such as oil. During a second part of the rotation cycle, the area between the rotors decreases, causing compression. During the compression period, fluid is pumped out of the pump at the outlet.

A typical automotive engine requires the largest amount of oil per engine revolution at idle speeds and a smaller amount of oil per engine revolution at higher engine speeds. Since the gerotor pump continues to deliver a fixed amount of oil per engine revolution, more oil is delivered to the engine at higher engine speeds than is actually required. For example, known gerotor pumps deliver about double the amount of oil required at very high engine speeds. The “surplus” oil must be returned to the engine oil pump through a pressure-regulating valve. Otherwise, oil pressure will become excessive at higher engine speeds.

Therefore, there is a need in the art to improve upon positive displacement pumps that relieve excess pressure and capacity through a relief valve. Accordingly, a need exists for an oil pump that is capable of operating without a pressure regulating valve to minimize the delivery of excess oil. Furthermore, a need exists for a pump capable of pumping and/or transferring a reduced amount of oil per engine revolution at higher engine speeds. In addition, a need exists for a gerotor pump having a movable outer rotor to adjust the amount of oil transferred from the pump per revolution.

SUMMARY OF THE INVENTION

The present invention provides an oil pump capable of reducing the amount of oil pumped per revolution so as not to pump excess oil at high engine speeds. Specifically, the present invention relates to a variable displacement gerotor pump capable of providing variable amounts of oil per revolution of the engine. In known gerotor pumps, the position of the outer rotor is fixed. As a result, the gerotor rotates to transfer a fixed amount of fluid per revolution.

However, the present invention advantageously provides a movable outer rotor that changes the amount of fluid transferred per gerotor revolution. Therefore, the present invention eliminates, or at least minimizes, the pumping of excess oil. In addition, the present invention has the potential to eliminate the pressure-regulating valve. In a vehicle, for example, the present invention reduces fuel consumption by reducing drive horsepower required to operate the pressure regulating valve and the gerotor pump.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

Objects and advantages together with the operation of the invention may be better understood by reference to the following detailed description taken in connection with the following illustrations, wherein:

FIG. 1 illustrates a pump having a winged portion in an embodiment of the present invention.

FIG. 2 illustrates the pump of FIG. 1 at a rotated position.

FIG. 3 illustrates an interior view of the pump of FIGS. 1 and 2.

FIG. 4 illustrates a pump having an eccentric ring and a winged portion in an embodiment of the present invention.

FIG. 5 illustrates a pump having an outer rotor movable with respect to the inner rotor.

FIG. 6 illustrates a pump having a relief channel in an embodiment of the present invention.

FIG. 7 illustrates an exploded view of the pump o FIG. 6 whereby an eccentric ring engages a rack.

FIG. 8 illustrates the pump of FIG. 7 at a rotated position.

FIG. 9 illustrates a pump having a divider in an embodiment of the present invention.

FIG. 10 illustrates the pump of FIG. 9 whereby the divider is shown in phantom.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is described as being implemented for use in an engine to, for example, pump oil; however, it is clearly contemplated that the present invention may be incorporated into other systems and may be used to pump other fluids as known to one of ordinary skill in the art. The present invention advantageously responds to increasing fluid pressure by reducing output flow. For example, the higher the oil pressure, the lower the rate of pumping of the fluid of the present invention.

As illustrated in FIGS. 1 and 2, a variable displacement pump 3, such as a gerotor pump, may have an inner rotor 5 (or gerotor) in meshed engagement with an outer rotor 7. The inner rotor 5 may rotate with respect to the outer rotor 7. For example, the inner rotor 5 may rotate in a counterclockwise direction. Of course, the present invention could be implemented such that the gerotor 5 rotates in a counterclockwise direction or other direction as will be appreciated by one of ordinary skill in the art.

The gerotor 5 may have teeth 9 in meshing engagement with notches 11 of the outer rotor 7. In a preferred embodiment, the outer rotor 7 has more notches 11 than the inner rotor 5 has teeth. In an exemplary embodiment, the outer rotor 7 has at least one more notch 11 than the inner rotor 5 has teeth 9. FIG. 1 illustrates an embodiment of the invention where the inner rotor 5 has eight teeth 9 and the outer rotor 7 has nine notches 11. The present invention should not be deemed as limited to any specific number or shape of the teeth 9 and/or the notches 11.

The variable displacement pump 3 responds to increasing pressure by lowering output flow. In such an embodiment, the higher the pressure present in the variable displacement pump 3, the less fluid may be pumped per revolution. The pump 3 may continue to pump a reduced amount of fluid per revolution until a predetermined amount of fluid per engine revolution is achieved and/or a predetermined output or input pressure is achieved. Therefore, the present invention eliminates the need for a pressure regulating valve.

The teeth 9 of the inner rotor 5 may be supported for rotation about a predetermined axis, as illustrated in FIGS. 1 and 2. The outer rotor 7 is movable about an axis that is spaced from the predetermined axis of the teeth 9 so as to provide the necessary eccentricity for proper operation of the variable displacement pump 3. The teeth 9 and the notches 11 cooperate to define a plurality of variable volume pumping chambers 13 whereupon during rotation of the inner rotor 5, at least one of the chambers 13 increases in volume to a maximum volume. Each of the notches 11 has a corresponding chamber 13 that changes in volume as the inner rotor 5 rotates. Continued rotation of the inner rotor 5 may then decrease the volume of a number of the chambers 13 to move fluid therethrough.

FIGS. 1 and 2 further illustrate a pump housing 15 for supporting the inner rotor 5 and the outer rotor 7. The pump housing 15 has an inlet 17 in fluid communication with an outlet 19. Fluid, such as oil, enters and/or fills the inlet 17 to provide fluid to the pump 3. Fluid enters at the inlet 17 and is pumped to the outlet 19 by the meshing engagement of the inner rotor 5 and the outer rotor 7. As the inner rotor 5 rotates, the chambers 13 of the pump 3 may be exposed to the inlet 17 so that fluid fills the chambers 13. For example, the fluid distributes at the inlet 17 to the chambers 13 between the inner rotor 5 and the outer rotor 7. The outlet 19 gathers and/or collects the fluid from the chambers 13 as each of the chambers 13 collapses at the outlet 19. In an embodiment, fluid may enter and/or may fill the chambers 13 at the inlet 17 by, for example, vacuum suction created by the rotation of the inner rotor 5.

As the inner rotor 5 rotates with respect to the outer rotor 7, the chambers 13 are continuously forming and continuously collapsing at opposing sides of the inner rotor 5. More specifically, the inner rotor 5 rotates from a point of closest proximity with the outer rotor 7 to a point of maximum distance to the outer rotor 7, as illustrated in FIGS. 1-3. In an exemplary embodiment, the outer rotor 7 is positioned such that the chambers 13 gather a maximum amount of fluid at the inlet 17 and move a maximum amount of the fluid to the outlet 19. At such a maximum displacement position, the pump 3 is displacing a maximum amount of fluid per revolution by, for example, exposing a maximum amount of the inlet 17 to the chambers 13. In such a position, a maximum amount of fluid may fill the chambers 13 at the inlet 17 and a maximum amount of fluid is capable of exiting the pump 3 at the outlet 19.

However, at high engine speeds, the inner rotor 5 may rotate at similarly high rates of speeds as a result of being connected to the crankshaft. Accordingly, more fluid is transferred from the inlet 17 to the outlet 19 than may be required by, for example, an engine. In operation, the inner rotor 5 may connect to the crankshaft of an internal combustion engine (not shown) and may rotate at a fixed speed in the idle condition, thereby causing pumping action. As such, the pumping action pulls oil from the inlet 17 to the outlet 19. This pumping action may occur at idle speeds and a constant pressure may be achieved. When the crankshaft speed increases during acceleration, the pumping action increases thereby increasing the oil pressure. Generally, as the rotation of the crankshaft increases, the oil and oil pressure required to operate the engine do not increase at the same rate. Advantageously, the present invention allows a reduction in the amount of fluid transferred from the inlet 17 to the outlet 19 per revolution of the inner rotor 5.

When assembled, the inner rotor 5 may be positioned within the pump housing 15 and an eccentric ring 20. In an embodiment, the eccentric ring 20 surrounds the outer rotor 7. The eccentric ring 20 may have a variable thickness about the perimeter. As shown in FIGS. 1-3, the eccentric ring 20 includes a wing or piston 22 that extends from the perimeter of the eccentric ring 20. The wing 22 may extend away from the inner rotor 5.

The outer rotor 7 may be positioned within the eccentric ring 20. To this end, the eccentric ring 20 may cradle and/or otherwise engage the outer rotor 7 such that movement of the eccentric ring 20 causes movement of the outer rotor 7. In known gerotor pumps, the outer rotor 7 is fixed. The outer rotor 7 of the present invention, however, is movable with respect to the pump housing 15 and/or the locations in which fluid enters and exits the pump housing 15. Movement of the outer rotor 7 changes the geometry and/or relative position in which the inner rotor 5 engages the outer rotor 7. Varying the geometry or relationship between the outer rotor 7 and the inner rotor 5 affects pumping effectiveness. For example, moving the outer rotor 7 changes the position in which the chambers 13 enlarge and collapse. To this end, changing the position of the outer rotor 7 will change the location in which the chambers 13 may have a maximum volume in relation to the inlet 17 and the outlet 19, and, in turn, change the amount of fluid transferred per revolution of the inner rotor 5.

Advantageously, the movable outer rotor 7 enables the pump 3 to operate at different rates and in different manners than presently known gerotor pumps. For example, the outer rotor 7 is movable to positions where the pump 3 displaces a predetermined amount of fluid per revolution of the gerotor 5. In addition, the outer rotor 7 may move to change the amount of fluid transferred per revolution of the inner rotor 5 automatically. In an embodiment, the outer rotor 7 may move in response to the pressure of the fluid at the outlet 19.

The outer rotor 7 may be initially set at a position (e.g., “maximum displacement position”) in which a maximum amount of the inlet 17 and the outlet 19 are exposed to the pump 3. At the maximum displacement position, the pump 3 is displacing a maximum amount of fluid per revolution of the inner rotor 5. In an embodiment, the eccentric ring 20 may be in a maximum displacement position as illustrated in FIGS. 1 and 3. Rotating the eccentric ring 20, for example, counter-clockwise positions the outer rotor 7 at a less efficient position. The eccentric ring 20 may rotate the outer rotor 7 along a range of positions from the maximum displacement position to a minimal displacement position, and in an embodiment, a reverse displacement position. At the reverse displacement position, the pump 3 may be transferring fluid from the outlet 19 to the inlet 17. The eccentric ring 20 may position the outer rotor 7 at the minimal displacement position in which the fluid from the inlet 17 merely churns within the body of the pump 3 or where little fluid enters the pump 3 from the inlet 17. At the minimal displacement position, the pump 3 may displace relatively little to no fluid per revolution of the inner rotor 5.

FIG. 2, for example, illustrates a rotated position of the outer rotor 7 and the eccentric ring 20. In such an embodiment, the eccentric ring 20 and the outer rotor 7 may be at the maximum displacement position as illustrated in FIGS. 1 and 3. To this end, the rotated position as illustrated in FIG. 2 may be a less efficient (e.g., reduced displacement) position, such as, a position in which the pump 3 transfers less fluid per revolution of the inner rotor 5 than the amount of fluid transferred at the maximum displacement position. The outer rotor 7 may be positionable between the maximum displacement (e.g., non-rotated position) and a reduced displacement position (e.g., rotated position). The present invention should not be deemed as limited to any specific position corresponding to any specific amount of fluid transferred per revolution. One of ordinary skill in the art will appreciate numerous orientations of the outer rotor 7 with respect to the inner rotor 5 that may be used for various applications.

As the crankshaft speed increases, the fluid pressure within the body 15 of the pump 3 may increase, including the pressure at the outlet 19. At a predetermined amount of pressure at the outlet 19, fluid may enter an opening 24 that is in fluid communication with the wing 22. To this end, the fluid pressure at the outlet 19 increases to move the wing 22. Pressure may reach a predetermined amount prior to movement of the wing 22.

In an embodiment, a biasing member 26 engages the wing 22 to resist movement until the predetermined pressure is met. The biasing member 26 may apply a threshold amount of force onto the wing 22. When the force exerted on the wing 22 exceeds the threshold force exerted by the biasing member 26, the wing 22 may move the eccentric ring 20. To this end, as outlet demand is reduced and oil pressure increases at the outlet 19, the eccentric ring 20 rotates to a less effective pumping position until equilibrium is achieved. For example, as pressure rises, the wing 22 may move the outer rotor 7 from the maximum displacement position to a reduced displacement position in which fluid displaced per revolution is less than the amount of displacement at the maximum displacement position. When the pressure decreases, the biasing member 26 acts to return the eccentric ring 20 towards the initial position (e.g., the maximum displacement position).

Accordingly, the present invention eliminates the need for a pressure-regulating valve to divert high-pressure fluid from the variable displacement pump 3. Advantageously, excess pressure at the outlet 19 is eliminated or at least reduced by movement of the eccentric ring 20 and/or the outer rotor 7. The biasing member 26 may be, for example, a spring, a piston or other type of biasing member as will be appreciated by one of ordinary skill in the art. Therefore, the rotatable eccentric ring 20 of the present invention addresses supply and demand concerns by pivoting to a variable pumping effectiveness position.

Advantageously, the movable outer rotor 7 enables the pump 3 to operate at different rates and in different manners than presently known gerotor pumps. For example, the outer rotor 7 is movable to positions where the pump 3 displaces less fluid per revolution of the gerotor 5. At lower engine speeds, for example, the engine requires that the pump 3 transfer a greater amount of oil per revolution, than the engine requires per revolution at high engine speeds. Due to this, the pump 3 self-regulates by moving the outer rotor 7 from the maximum displacement position to a reduced displacement position at higher engine speeds. Specifically, at the reduced displacement position, a portion of the fluid filling the chambers 13 retreats back to the inlet 17 resulting in a decreased fluid flow at the outlet 19. More specifically, the outer rotor 7 moves such that the size of the chambers 13 collapsing at the outlet 19 at the reduced displacement position are smaller than the size of the chambers 13 collapsing at the outlet 19 at the maximum displacement position.

The present invention allows the outer rotor 7 to move automatically in response to changes in discharge pressure (e.g., pressure at the outlet 19). That is, the outer rotor 7 moves from the maximum displacement position to a reduced displacement position to correspond to the needs of the engine while eliminating, or at least minimizing surplus oil.

FIG. 4 illustrates another embodiment of the present invention. A pump 70 having an eccentric ring 72, a wing portion 74 and a fluid pocket 76. The pump 70 receives fluid from the inlet 78 and transfers and/or pumps the fluid to the outlet 80. The inlet 78 and the outlet 80 may operate as “kidneys” or headers to provide and to receive fluid, as the fluid enters and exits the pump 70. Varying the geometry or relationship between the moving parts relative to the inlet 78 and the outlet 80 may affect pumping effectiveness. For example, moving the outer rotor changes the position in which the chambers between the inner rotor and outer rotor enlarge and collapse relative to the inlet 78 and the outlet 80. The outer rotor may be positioned within the eccentric ring 72. To this end, the eccentric ring 72 may cradle and/or otherwise engage the outer rotor such that movement of the eccentric ring 72 causes movement of the outer rotor.

As illustrated in FIG. 4, the wing portion 74 is attached to and/or integrally formed with the eccentric ring 72. In an embodiment, the wing portion 74 may be surrounded on the three sides. For example, the wing portion 74 may be surrounded on two sides by the pump body and the remaining side by the pump cover, (not shown) when installed. As the pump 70 operates, a portion of the fluid from the outlet 80 is piped to and/or otherwise in fluid communication with the fluid pocket 76. When the pressure at the outlet 80 reaches a predetermined level, the wing portion 74 (and thus the eccentric ring 72) rotates to change the orientation of the outer rotor with respect to the inner rotor.

The eccentric ring 72 may have teeth 82 that are capable of engagement with a rack 84, as shown in FIG. 4 above the eccentric ring 72. The pressure from the outlet 80 may cause the eccentric ring 72 to rotate and, in turn, force the rack 84 to move. In an embodiment, the rack 84 resists movement of the eccentric ring 72 such that the eccentric ring 72 rotates at a predetermined amount of pressure at the outlet 80 and/or a predetermined amount of pressure in the fluid pocket 76.

To this end, the rack 84 may have a biasing member 86, such as a spring for resisting movement of the rack 84 and/or the eccentric ring 72. As the oil pressure moves the eccentric ring 72, the rack 84 compresses the biasing member 86 that resists the force initiated from the eccentric ring 72. The movement of the eccentric ring 72 moves the outer rotor from a position of maximum displacement to a position that causes the pump 70 to deliver less fluid volume per revolution. Specifically, the location of the chambers formed between the gerotor and the outer rotor move from the maximum displacement position to a less efficient position, for example, toward the inlet 78 of the pump 70. The meshing engagement of the gerotor and the outer rotor squeezes the fluid into the outlet 80.

The further the eccentric ring 72 rotates, the less fluid enters the pump 70 at the inlet 78. As a result, the further the eccentric ring 72 rotates, the less fluid transffere to the outlet 80. When oil pressure subsequently drops (e.g. such as when the engine speed lowers), the stored potential energy of the biasing member 86 acts to expand and push the rack 84, for example, from left to right as illustrated in FIG. 4, to move the eccentric ring 72. In a preferred embodiment, the rack 84 imparts a rotational force on the eccentric ring 72 through the meshed engagement of teeth 82 of the eccentric ring 72 with the rack 84. If the pressure falls below a predetermined level, the rack 84 returns the eccentric ring 72 toward the maximum displacement (or greatest fluid output per revolution) position.

FIGS. 6-8 illustrate another embodiment of the present invention. In such an embodiment, a pump 100 having an eccentric ring 102 is generally illustrated. The pump 100 may have an inner rotor 104 and an outer rotor 106 in meshed engagement for moving fluid there through. The pump 100 may receive fluid from an inlet 108 and pump or otherwise transfer such fluid to an outlet 110.

The outer rotor 106 may be positioned within the eccentric ring 102. To this end, the eccentric ring 102 may cradle and/or may otherwise engage the outer rotor 106 such that movement of the eccentric ring 102 causes movement of the outer rotor 106. The eccentric ring 102 is in engaged with a rack 112. For example, the rack 112 engages teeth 114 in the eccentric ring 102 to move and/or rotate the eccentric ring 102. As set forth above, rotation of the eccentric ring 102 changes the orientation of the outer rotor 106 with respect to the inner rotor 104. Changing the orientation changes the amount of fluid displaced from the pump 100 per revolution of the inner rotor 104.

The pump 100 has a relief channel 120 that is in fluid communication with the outlet 110. In addition, the relief channel 120 may be in fluid communication with the rack 112 such that pressure from the relief channel 120 is applied to the rack 112. At a predetermined level of pressure, a biasing member 122 within the rack 112 is compressed such that the rack 112 moves linearly to rotate the eccentric ring 102 and/or the outer rotor 106.

To this end, the relief channel 120 receives the pressure of the fluid from the outlet 110. At low discharge pressures, such as when the engine is idle or at a lower engine speed, the outer rotor 106 is at or near the maximum displacement position. Conversely, as the pressure at the relief channel 120 increases, such as at high engine speeds, the force of the pressure at the relief channel 120 moves the biasing member 122, the rack 112 and thus the outer rotor 106 to the reduced displacement position. The pressure at the channel 120 forces the outer rotor 106 to remain at the reduced displacement position while the pressure is equal to or greater than the force of the biasing member 122. If the pressure at the relief channel 120 decreases below the force of the biasing member 122, the outer rotor 106 may move back toward the maximum displacement position.

As the speed of the engine and the pressure at the relief channel 120 (and the outlet 106) subsequently rise and fall, the position of the outer rotor 106 responds to change the rate of fluid per revolution as required by the engine. For example, the eccentric ring 102 and the outer rotor 106 rotate to reduce the amount of fluid pumped per revolution of the inner rotor 104, as illustrated in FIG. 7. Therefore, the present invention enables the pump 100 to be self-regulating and vary the amount of oil or fluid transferred per revolution. When the pressure drops completely, such as, when the engine is shut off, the outer rotor 106 moves or rotates to the maximum displacement position, such as, to the left as illustrated in FIGS. 6 and 8. Upon ignition of the engine, the pump 100 may initially operate at the maximum displacement position.

Therefore, the present invention preserves energy. With respect to the pump 100, the energy required is directly related to the amount of fluid pumped compared to the delivery pressure. As set forth above, the present invention limits the pumping of surplus oil by reducing the oil transferred per engine revolution at higher engine speeds.

The relief channel 120 may terminate at the rack 112. In a preferred embodiment, the channel 120 pressurizes the rack 1 12 and the spring 122 to move the rack 112 that in turn moves the eccentric ring 102 and the outer rotor 106. In one embodiment, the relief channel 120 may be capable of fluid communication with the inlet 108 to circulate the portion of the outlet fluid entering the relief channel 120. In such an embodiment, the channel 120 may act or serve as a pressure relief valve at certain conditions, such as, at cold conditions as will be appreciated by one of ordinary skill in the art.

FIG. 5 illustrates another embodiment of the present invention. A pump 50 has an inlet 53 in fluid communication with an outlet 51. The pump 50 may have a pump housing 52, an inner rotor 54 and a movable outer rotor 56. The outer rotor 56 is movable with respect to the inner rotor 54 to change the amount of fluid transferred per revolution of the inner rotor 54. For example, the outer rotor 56 moves from the maximum displacement position to a reduced displacement position to correspond to the requirements of an engine while eliminating, or at least minimizing, surplus oil. At low discharge pressures, such as when the engine is idle or at a lower speed, a biasing component, such as the biasing member 26 of FIGS. 1-3, may bias or force the outer rotor 56 toward the maximum efficient position.

As shown in FIG. 5, the outer rotor 56 may have an enlarged body 60 for moving the outer rotor 56 with respect to the inner rotor 54. In one embodiment, the body 60 surrounds the outer rotor 56, and may be integrally formed with the outer rotor 56. A plurality of protruding members 62 may protrude from the body 60. The protruding members 62 may engage the pump housing 52 to properly orientate the outer rotor 56 with respect to the inlet 53 and the outlet 51.

The pressure at the outlet 51 may automatically move the outer rotor 56. For example, as the pressure at the outlet 51 increases, such as, at high engine speeds, the outer rotor 56 may move automatically to a reduced displacement position. In an embodiment, the outer rotor 56 may overcome the force of the biasing member at a predetermined pressure at the outlet 51 prior to moving to a reduced displacement position. The biasing member may force the outer rotor 56 to the maximum displacement position until the pressure at the outlet 51 is substantially equal to the predetermined pressure. In response, the pressure at the outlet 51 may automatically overcome the force of the biasing member to move the outer rotor 56 to a reduced displacement position.

As the speed of the engine and the pressure at the outlet 51 subsequently rise and fall, the position of the outer rotor 56 responds to change the rate of fluid per revolution as required by the engine. Therefore, the biasing member enables the pump 50 to be self-regulating and vary the amount of oil or fluid transferred per revolution. To this end, the body 60 of the outer rotor 56 may move automatically in response to pressure at the outlet 51. The body 60 may rotate in response to the pressure at the outlet 51 and/or the pressure at the inlet 53. Accordingly, the biasing member may be incorporated to bias the body 60 and, thus, the outer rotor 56 in response to pressure at the inlet 53 and/or the outlet 51. When the pressure drops completely, such as, when the engine is shut off, the outer rotor 56 moves or rotates to the position of maximum efficiency, such as, to the left, as illustrated in FIG. 5. Upon ignition of the engine, the pump 3 will begin operating in the most efficient position. Accordingly, FIG. 5 illustrates an embodiment of the invention whereby the outer rotor 56 automatically moves in response to pressure at the inlet 53 and/or the outlet 51.

FIGS. 9 and 10 illustrate another embodiment of the invention. As shown in FIGS. 9 and 10, a pump 200 has an inlet 205 in fluid communication with an outlet 207. A divider 208 is positioned between the inlet 205 and the outlet 207. The divider 208 may be, for example, a slug, a plateau or other member capable of limiting capacity of an inlet and/or an outlet as will be appreciated by one of ordinary skill in the art.

In typical gerotor pumps, the divider is fixed and/or the divider is incorporated into the pump housing. Advantageously, however, the divider 208 is movable within the pump 200 to change an amount of fluid entering the inlet 205 and/or exiting the outlet 207. As illustrated in FIG. 10, the divider 8 is moveable between the inlet 205 and the outlet 207.

As mentioned, at high engine rates, oil pressure at the pump 200 increases yet less fluid is actually required. The present invention reduces the size of the inlet 205 to reduce the amount of fluid exiting the outlet 207. Specifically, as pressure increases, the divider 208 is forced toward the inlet 205 to reduce the size (or volume capacity) of the inlet 205. In an exemplary embodiment, the divider 208 rotates about 75 degrees clockwise at a maximum pressure to reduce the inlet 205 to about 25% of its original volume. At the rotated position of the divider 208, the amount of fluid output is reduced due to the pump 200 having a limited portion of volume capacity at the inlet 205.

A biasing member may be operably connected to the divider 208 to return the divider 208 to the low pressure end of the pump 200 from a displaced position at the high pressure end. For example, the biasing member may store energy as the divider 208 is forced to rotate in a clockwise direction or otherwise move the divider 208 such that the size of the inlet 205 is reduced. Upon a drop of pressure, the biasing member forces the divider 208 back to an initial position or a position that increases the size of the inlet 205.

As pressure at the pump 200 decreases, such as at a lower engine rate, the divider 208 is movable to increase the size or volume capacity at the inlet 205. To this end, the divider 208 is movable to a position in which the pump 200 is at the maximum displacement position. In an exemplary embodiment, the stored energy (e.g. potential energy) of the biasing member from the movement at the high fluid pressure is released to move the divider 208 to its initial position.

Although the preferred embodiment of the present invention has been illustrated in the accompanying drawing and described in the foregoing detailed description, it is to be understood that the present invention is not to be limited to just the preferred embodiment disclosed, but that the invention described herein is capable of numerous rearrangements, modifications and substitutions without departing from the scope of the claims hereafter. 

1. A variable displacement pump for transferring fluid from an input to an output, the pump comprising: an inner rotor; an outer rotor in meshing engagement with the inner rotor; and a body extending from the outer rotor, the body connected to the outer rotor such that movement of the body causes movement of the outer rotor, the body automatically movable in response to changes in fluid pressure at the output.
 2. The variable displacement pump of claim 1 wherein the body is freely movable in response to pressure at the output.
 3. The variable displacement pump of claim 1 wherein the body is an eccentric ring.
 4. The variable displacement pump of claim 3 further comprising: a wing portion extending from the eccentric ring, the wing portion capable of moving the outer rotor.
 5. The variable displacement pump of claim 4 further comprising: a rack and pinion engaging said eccentric ring, the rack and pinion preventing movement of the eccentric ring below a predetermined pressure.
 6. The variable displacement pump of claim 1 further comprising: a biasing member preventing movement of the outer rotor if the fluid pressure at the output is below a predetermined fluid pressure.
 7. The variable displacement pump of claim 6 wherein a portion of the fluid at the output is in fluid communication with the biasing member.
 8. The variable displacement pump of claim 7 further comprising: a fluid pocket in fluid communication with the output, the fluid pocket receiving a portion of the fluid at the output.
 9. The variable displacement pump of claim 8 wherein the fluid pocket is a relief channel.
 10. The variable displacement pump of claim 9 further comprising: a rack in fluid communication with the relief channel, the rack capable of moving the outer rotor if the fluid pressure at the rack is above a predetermined pressure.
 11. The variable displacement pump of claim 10 further comprising: a biasing member providing a threshold force to the rack to prevent movement of the outer rotor if the fluid pressure is less than the predetermined pressure.
 12. A variable displacement pump for transferring fluid from an input to an output, the pump comprising: an inner rotor having a plurality of teeth; an outer rotor having a plurality of notches for receiving said teeth, said inner rotor and said outer rotor capable of meshingly engaging to transfer said fluid from said input to said output; a channel in fluid communication with said output, said channel capable of causing movement of said outer rotor at a predetermined pressure at the output.
 13. The variable displacement pump of claim 12 further comprising: a wing portion in fluid communication with said channel, the wing portion capable of moving the outer rotor at a predetermined fluid pressure in the channel.
 14. The variable displacement pump of claim 13 further comprising: an eccentric ring to engages the outer rotor and the wing portion, wherein the wing portion moves the eccentric ring and the outer rotor at the predetermined fluid pressure.
 15. The variable displacement pump of claim 14 further comprising: a rack and pinion engaging said eccentric ring, the rack and pinion preventing rotation of the eccentric ring below a predetermined fluid pressure.
 16. The variable displacement pump of claim 14 wherein the eccentric ring has a variable thickness.
 17. A variable displacement pump comprising: a pump body having an inlet and an outlet; an inner rotor positioned within the pump body, the inner rotor rotating within the pump body; an outer rotor in meshing engagement with the outer rotor to transfer fluid from the inlet to the outlet; an eccentric ring engages the outer rotor, the eccentric ring movable with respect to the inner rotor, the eccentric ring capable of causing movement of the outer rotor with respect to the inner rotor; and a channel in fluid communication with the outlet, the channel causing movement of the eccentric ring at a predetermined pressure at the outlet, the movement of the eccentric ring changing the amount of fluid transferred from the inlet to the outlet per revolution of the inner rotor.
 18. The variable displacement pump of claim 17 further comprising: a wing portion attached to the eccentric ring, the pressure at the outlet capable of moving the wing portion and the eccentric ring.
 19. The variable displacement pump of claim 17 wherein the outer rotor moves automatically in response to changes in fluid pressure at the outlet.
 20. The variable displacement pump of claim 17 further comprising: a biasing member preventing movement of the eccentric ring below the predetermined pressure. 